2008 Mercedes CLK350 Fuel Pump Location: Where It Is and How to Access It

The bottom line up front: On a 2008 Mercedes-Benz CLK350, the main electric fuel pump is located inside the fuel tank on the right (passenger) side of the car, and you access it by removing the rear seat cushion and lifting the access panel beneath it. There is also a secondary fuel transfer unit on the left (driver) side behind the rear seat, but that unit mainly moves fuel from one side of the saddle-style tank to the other and is not the main pump that feeds the engine.

If your CLK350 cranks but will not start, stalls under load, or makes a loud whine from the rear seat area, the fuel pump is a prime suspect. Below is everything you need to know about locating, diagnosing, and replacing the fuel pump on your 2008 CLK350 — including the exact steps to reach it, the tools you will need, and what to look for when buying a replacement.

Why the Location Matters

The 2008 CLK350 uses what is called a "saddle" style fuel tank. This means the tank wraps around the driveshaft, creating two separate halves — a left side and a right side. The main electric fuel pump, the one that delivers pressurized fuel to the engine, sits inside the right half of the tank. A secondary unit on the left side helps transfer fuel over to the right side so the main pump never runs dry.

This two-pump layout confuses many owners. Some parts websites call the left-side unit a "fuel pump," but in most cases it is a transfer unit or fuel level sender, not the main pump. If your engine is not getting fuel at all, the problem is almost always on the right side.

How to Confirm It Is the Fuel Pump

Before you start pulling apart the rear seat, take a few minutes to confirm the fuel pump is actually the problem. A failed pump shares symptoms with other fuel system faults, so a quick check can save you hours of work.

Common signs of a failing fuel pump on a 2008 CLK350:

  1. Engine cranks but does not start. The starter turns the engine over, but it never fires up.
  2. Engine stalls while driving. The car dies unexpectedly, often under load or acceleration, and may not restart for a while.
  3. Loud whining noise from the rear seat. A high-pitched buzz from the fuel tank area, especially when you first turn the ignition on, points to a struggling pump.
  4. Sputtering or hesitation during acceleration. The engine feels like it is not getting enough fuel at higher speeds.

Quick test you can do yourself:

  • Locate the Schrader valve on the fuel rail (the metal line that distributes fuel to the injectors). It looks like a tire valve.
  • Press the small pin inside the valve with a screwdriver. If little or no fuel sprays out, you likely have a fuel delivery problem.
  • You can also spray starting fluid into the intake. If the engine runs for a few seconds on the fluid and then dies, the issue is almost certainly the fuel pump or fuel delivery system, not the ignition or engine itself.

A shop will typically confirm the diagnosis with a fuel pressure gauge. On a 2008 CLK350, fuel pressure at idle should be in the range of roughly 47–55 PSI. If the pressure is well below spec or does not build at all when the ignition is turned on, the pump needs attention.

Where Exactly Is the Fuel Pump Located?

Once you have confirmed a fuel delivery issue, here is exactly where to look on your 2008 CLK350.

Right side (passenger side) — main fuel pump:

  • The main pump is under the rear passenger-side seat.
  • You will see a metal or plastic access cover in the floor pan beneath the seat cushion.
  • Removing this cover exposes the top of the fuel pump module, which includes the pump, the fuel level sender, and the fuel lines.

Left side (driver side) — transfer unit:

  • There is a similar-looking unit under the rear driver-side seat.
  • This is the fuel transfer unit that moves fuel from the left side of the saddle tank over to the right side, where the main pump sits.
  • Some aftermarket sites sell a "left fuel pump" for this position; in many cases it is a transfer pump, not the main pressure pump.

An important note: On some related Mercedes models, the fuel pump is mounted on the driver side depending on the year and configuration. For the 2008 CLK350 specifically, the main pump is on the passenger side. However, if you are unsure, confirm with your VIN before ordering parts.

Step-by-Step: How to Access the Fuel Pump

Replacing the fuel pump in a CLK350 is a moderately involved DIY job. Most owners with basic mechanical skills can handle it in about two to three hours. Follow these steps carefully.

Tools and parts you will need:

  • 13 mm socket or wrench for the seat bolts
  • 8 mm socket for the access panel screws
  • Flathead screwdriver
  • Fuel pump collar removal tool (a large spanner or specialty tool for the retaining ring)
  • New fuel pump module
  • New rubber sealing ring (O-ring) for the pump assembly
  • Fuel pressure gauge (for verification)
  • Container and rags for any fuel spillage

Step 1: Disconnect the battery.

Always disconnect the negative battery terminal before working near fuel system components. This prevents accidental sparks and electrical shorts.

Step 2: Relieve fuel system pressure.

Remove the fuel pump relay or fuse, then crank the engine for a few seconds until it stalls. This releases the pressure in the fuel lines. You can also simply remove the fuel cap to release any residual tank pressure.

Step 3: Remove the rear seat cushion.

On the CLK350, there are two clips at the front edge of the rear seat, roughly where your calves would rest. Pop these clips up with a screwdriver to access two nuts. These require a 13 mm socket or wrench. Once those nuts are off, lift the seat bracket forward and remove the seat cushion.

Step 4: Lift the sound deadening material.

Under the seat cushion, there is a layer of protective sound insulation. Lift or pull it out of the way to see the metal floor pan and the access cover beneath.

Step 5: Remove the access cover.

You will see a black or metal cover plate. It is held in place by several small screws — typically 8 mm. Remove them and gently pry up the cover.

Step 6: Disconnect the electrical connector and fuel lines.

You will now see the top of the fuel pump module. Before removing anything, take a picture with your phone. This will help you remember the orientation of the pump, the fuel lines, and the electrical connector when you reinstall everything.

Carefully disconnect the electrical connector and the fuel lines from the pump assembly. Expect some fuel to spill out; have rags and a container ready.

Step 7: Remove the retaining collar and lift the pump out.

The pump assembly is held in place by a large threaded collar or ring. You will likely need a specialty fuel pump collar tool to loosen it — it is extremely tight and difficult to turn by hand. Once the collar is loose, carefully lift the entire pump module out of the tank, taking care not to damage the fuel level float arm.

Step 8: Install the new pump.

Fit the new pump module into the tank, making sure the orientation matches what you photographed. Replace the large rubber sealing ring (O-ring) with a new one — this is critical to prevent fuel leaks and fuel odors inside the cabin. Tighten the retaining collar securely, reconnect the fuel lines and electrical connector, and reinstall the access cover and rear seat.

What to Look For When Buying a Replacement Pump

The 2008 CLK350 fuel pump is available from Mercedes dealers, online OEM parts suppliers, and aftermarket brands. Prices for a used OEM unit run roughly $75 to $200, while new OEM or quality aftermarket pumps can cost more depending on the seller.

Check the following before you buy:

  1. Confirm the correct side. Make sure you are ordering the right-side main pump (part numbers such as 2094700294 or 2094700194) rather than the left-side transfer unit. The left-side transfer pump has different part numbers, such as 2094701394.
  2. Inspect used units carefully. If buying a used pump, check the electrical connector for signs of melting and ensure the plastic housing is not cracked.
  3. Know your vehicle's options. Some CLK350 models have FlexFuel capability (Code 929), while others do not. The correct pump can differ based on this option, so verify with your VIN before ordering.
  4. Replace the sealing ring. Always buy a new large rubber O-ring or sealing ring for the pump assembly. Reusing the old one risks fuel leaks and fuel smell in the cabin.

Why You Should Consider a KEMSO Fuel Pump

When the time comes to replace the fuel pump on your 2008 Mercedes CLK350, the brand you choose matters. A cheap, poorly built pump can fail again within months, leaving you stranded and forcing you to repeat the entire replacement job.

KEMSO offers a lineup of high-performance fuel pumps built as direct OEM replacements. That means they are designed to match the fit, form, and function of the original pump in your CLK350, so installation is straightforward and the performance matches what your engine expects.

KEMSO fuel pumps are engineered for clean, consistent fuel delivery and are built with quality materials to withstand the demands of daily driving. Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind that your replacement pump is protected for as long as you own your vehicle. If you are looking for a reliable replacement that will not let you down, KEMSO is a strong choice.

You can browse the full KEMSO lineup, including fuel pumps for your Mercedes CLK350 and many other vehicles, at:

https://www.kemsoracing.com/

Frequently Asked Questions

How long does a fuel pump last on a 2008 CLK350?

Most electric fuel pumps are designed to last 150,000 to 200,000 miles or more. However, running the tank low frequently, using contaminated fuel, and electrical issues can shorten pump life significantly. If your CLK350 has high mileage and is showing fuel system symptoms, a replacement pump is a reasonable preventive step.

Can I drive with a failing fuel pump?

It is not safe. A failing fuel pump can leave the vehicle stranded without warning, which is dangerous in traffic. A complete failure can also lead to an overheated engine and catalytic converter damage. If you suspect the pump is failing, address it promptly.

Is the fuel filter separate on a 2008 CLK350?

On many CLK350 models, there is no separate serviceable fuel filter along the fuel line. Instead, the fuel pump module includes a fine mesh screen or strainer that filters fuel before it enters the pump. On models with an external filter, it is usually replaced at the same time as the pump. If your car stalls and restarts after sitting, a clogged filter or screen may be the culprit.

Should I replace both fuel pumps?

Usually not. The right-side main pump is the one that feeds the engine. The left-side transfer unit only moves fuel across the saddle tank. If the engine is not getting fuel, the main pump is the problem in the vast majority of cases. A failing transfer unit can cause fuel starvation on the left side, but that is less common. Replace what is actually failing, and confirm the diagnosis before spending money on both sides.

Final Thoughts

Finding the fuel pump on a 2008 Mercedes CLK350 is not difficult once you know the layout. The main pump sits under the right rear seat, behind a removable access panel. The left-side unit is a transfer pump, not the primary fuel pump. With the right tools, a few hours of work, and a quality replacement pump, you can get your CLK350 running reliably again.

Remember to always confirm the exact part for your VIN, replace the sealing ring during installation, and choose a reputable brand. For a high-performance, OEM-replacement fuel pump backed by a lifetime warranty, be sure to check out KEMSO at https://www.kemsoracing.com/ before making your purchase.


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